[1] Field of the Invention
The present invention relates to stereotactic instruments used by surgeons to precisely introduce electrodes deep into the brain and more particularly to a stereotactic instrument which obviates the need to take many X-ray photos and correct them for beam spreading and rotation of the head in relation to the axis of the X-ray beam.
[2] Description of the Prior Art
Horsley and Clarke used stereotactic instruments on experimental animals as long ago as 1908 (Brain 31:45-124). Kirschner introduced use of stereotactic instruments for electrocoagulation in humans in 1933 (Arch. Klin. Chir. 176:581-620) and Spiegel and Wycis described their use in intracerebral surgery in 1947 (Science 106:349-350). Numerous other models have been described in neurological journals. Most, however, require radiological correction in use, cf. Mark, McPherson and Sweet, Am. J. Roentgenology 71:435-444 (1954).
Correction frequently requires calculation of how far an X-ray has diverged from the central axis of the beam by the time it passes through a particular part of the brain and strikes the film or detector. Such calculations, particularly if they must be done for each of a series of X-rays, undesirably prolong the surgical procedure and the length of time the patient spends under anesthesia. Frequently, X-rays must be repeated for each additional target.